Lawn string trimmers are widely used as a means to trim vegetation in areas not easily accessible to lawn mowers. However, conventional lawn string trimmers must be supported physically by the user above the ground so that the vegetation is trimmed at the desired height. Prolonged use of conventional lawn trimmers, therefore, is quite fatiguing.
In addition, it is difficult for a user to support the lawn trimmer to achieve a constant cutting height resulting in height variations of the cut vegetation. As a result, the use of lawn trimmers is typically reserved for those vegetation regions where such height variations will not be noticed and/or that cannot be reached by other powered trimming tools.
The art has recognized the problems associated with conventional lawn string trimmers briefly described above and has proposed a variety of devices which provide supplemental support for the lawn string trimmer during use. For example, in U.S. Pat. No. 4,894,916 to Nimz et al, a single wheel support structure is provided which is attached to the shaft of a lawn string trimmer so as to provide rolling support of the trimmer cutting head over the surface of the ground.
The wheel of the support structure proposed by the Nimz et al '916 patent, moreover, is oriented so that it remains in a plane that is parallel to the cutting plane of the trimmer's head. That is, according to the Nimz et al patent, the wheel is mounted for rolling movement to the plate bracket via a cotter pin which inserted through a rigidly fixed axle. As a result of such orientation, the support wheel of the Nimz et al '916 patent may be brought to bear against a vertical surface (in which case the trimmer's cutting head is supported in a horizontal plane) or a horizontal surface (in which case the trimmer's cutting head is supported in a vertical plane).
As can be appreciated from the prior art represented by the Nimz et al '916 patent, the orientation of the support wheel precludes movement of the string trimmer along the ground surface so as to trim vegetation along a substantially constant horizontal cutting plane in the absence of a vertical surface being present. Thus, the supplemental trimmer support structure proposed by the Nimz et al '916 patent is unsuitable for use in trimming vegetation in a relatively open space.
It would therefore be quite advantageous if supplemental support structures were provided which enables a lawn string trimmer to be supported a relatively fixed distance above the ground's surface and which could be rolled easily along such surface to allow a relatively open expanse of vegetation to be trimmed at a desired fixed height. It is towards providing structure which attains such advantages that the present invention is directed.
Broadly, the present invention is embodied in a wheeled support structure for lawn string trimmers whereby the support caster is oriented in a vertical plane which is perpendicular to the horizontal cutting plane of the string trimmer. More specifically, the present invention includes an elongate extension rod having an upper end fixed (preferably by means of a removable bracket assembly) to the shaft of the trimmer. A ground-engaging caster is mounted to the opposite end of the extension rod such that the extension rod (and hence the trimmer to which it is attached) is capable of swivelling movement relative to the ground.
The extension rod is of sufficient length so that the operator can maintain the cutting head of the trimmer in substantial parallel alignment with the ground. Moreover, as noted briefly above, the journalled attachment of the caster to the lower end of the extension rod is such that the caster wheel is oriented in a plane which at all times is transverse to the cutting plane of the trimmer head. In this manner, therefore, the support structure of this invention allows the operator to supportably move the trimmer over the ground and easily change the direction of such movement without disrupting the substantially parallel orientation between the cutting head and the ground being trimmed. As a result, the vegetation on the ground can be trimmed to a substantially uniform level.
Further aspects and advantages of this invention will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiment thereof.